Cam follower formed without removing any material

ABSTRACT

A finger lever for a valve train of an internal combustion engine, said finger lever being made by shaping without chip removal and comprising two side walls ( 5,6 ) which are connected to each other in a first end region ( 1 ) by a first bottom wall ( 4 ) to form an upwardly open U-shape, the first bottom wall ( 4 ) comprising a downwardly facing semi-spherical recess ( 7 ) for receiving a support element, said side walls ( 5,6 ) being connected to each other in a second end region ( 2 ) by a second bottom wall ( 11 ) to form an upwardly open U-shape, said second bottom wall ( 11 ) comprising a contact surface for a valve stem of a gas exchange valve ( 12 ), and the contact surface comprising lateral guides spaced apart from each other characterized in that, in the region of the contact surface of the valve stem ( 12 ) and/or in the region of the semi-spherical recess ( 7 ), the side walls ( 5,6 ) comprise partially punched-out sections ( 14 ) that are bent through nearly 180° toward the valve stem ( 12 ) and/or toward the support element respectively, so that retaining tabs ( 13 ) are formed for the lateral guidance of the finger lever on the valve stem ( 12 ) and/or on the support element

This application is a 371 of PCT/EP98/06381 filed Oct. 7, 1998.

FIELD OF THE INVENTION

The invention concerns a finger lever for a valve train of an internalcombustion engine, said finger lever being made by shaping without chipremoval and comprising two side walls which are connected to each otherin a first end region by a first bottom wall to form an upwardly openU-shape, the first bottom wall comprising a downwardly facingsemi-spherical recess for receiving a support element, said side wallsbeing connected to each other in a second end region by a second bottomwall to form an upwardly open U-shape, said second bottom wallcomprising a contact surface for a valve stem of a gas exchange valve,and the contact surface comprising lateral guides spaced apart from eachother.

BACKGROUND OF THE INVENTION

A generic finger lever of the pre-cited type having lateral guides isknown from U.S. Pat. No. 5,016,582. These guides bear against the valvestem of a gas exchange valve and have the function of guiding the fingerlever laterally, i.e. they prevent the finger lever from slipping offthe valve stem. These lateral guides are formed by a doubling of theside walls, i.e. the side walls merge at their lower ends into parallel,upwardly extending inner side walls that are connected to each other bya bottom wall. In this way, a downwardly facing recess is formed in thefinger lever for the valve stem, said recess being defined by the twoinner side walls and the bottom wall.

A drawback of this finger lever is that this type of lateral guidancenecessitates a complicated shaping procedure and the finger lever has alarge mass due to the doubling of the side walls.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved fingerlever whose lateral guides are substantially simpler to manufacture.

The invention achieves this object in that, in the region of the contactsurface of the valve stem and/or in the region of the semi-sphericalrecess, the side walls comprise partially punched-out sections that arebent through nearly 180° toward the valve stem and/or toward the supportelement respectively, so that retaining tabs are formed for the lateralguidance of the finger lever on the valve stem and/or the supportelement.

The advantage of this solution is, on the one hand, that the retainingtabs serving as lateral guides can be made with a negligible amount ofadditional work compared to the prior art by a simple punching andbending operation as a part of the general manufacturing process. On theother hand, the mass of the lever can be reduced because the retainingtabs originally form a part of the side walls and do not have to beformed out of additional material. Still another advantage is that theretaining tabs can be arranged both in the end region of the valve stemand in the end region of the support element. While the arrangement inthe end region of the valve stem is intended mainly for the lateralguidance of the finger lever on the valve stem, retaining tabs in theend region comprising the semi-spherical recess are to be understood aslateral safety devices for mounting that prevent a lateral tilting ofthe lever when it is brought into place before the mounting of thecamshaft. Such a tilting would otherwise be possible due to the factthat the center of gravity of the lever as a whole is situateddistinctly higher than the points of support.

The upper boundary of the punched-out section is situated below theupper edge of the side walls This means that the side walls from whichthe retaining tabs are punched out are not completely severed. Thisassures that a residual cross-section remains in the upper part of theside walls so that an adequate rigidity is maintained in the region ofthe pressure zone of the finger lever.

The shape of the upper edge of the side walls in the region of thepunched-out section is matched to the profile of the punched-outsection. This means that the side walls follow the profile of thepunched-out section so that, for example, if the punched-out section hasan arcuate configuration, the side walls will also have an arcuateshape. This enlarges the residual cross-section of the side walls andthus enhances the stability of the lever.

According to a further feature of the invention, the residualcross-section of the side wall formed by the partially punched-outsection is displaced into the pocket by the bent-over retaining tab.Thus, by a simple shaping operation, for example pressing, this residualcross-section is displaced toward the valve stem or toward the supportelement respectively, so that, on the one hand, the large cross-sectionwhich favors stiffness is approximately maintained and, on the otherhand, possible problems in free movement due to the enveloping circle ofthe cam, especially in the case of miniaturized levers, are avoided.

According to a further additional feature of the invention, theretaining tabs may have a rectangular, a trapezoid or a semicircularconfiguration. These are all equally efficient forms and the choicedepends only on tool availability and suitability for the particularcase of use. One factor to be kept in mind when choosing the shape ofthe retaining tab is that the most favorable possible distribution ofstress in the residual cross-section should be achieved.

The retaining tabs may be subjected to an after-treatment of stamping.By this is meant that a modification of the cross-section is effected bya subsequent shaping process, so that the surface area of the retainingtab is enlarged, for example, by ironing.

It can be advantageous if the retaining tabs are parallel to or are bentto extend at a defined angle to the side walls. If the retaining tabsare parallel to the side walls, they are advantageously arrangedinwardly offset from the side walls.

Finally, the upper edges of the side walls in the region in front of andbehind the retaining tabs is bend inward at a right angle. This inwardbending makes up for the loss of stiffness caused by the punching out ofthe retaining tabs.

The invention will now be described more closely with the help of thefollowing example of embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a finger lever, partly in section,

FIGS. 2 and 3 show a section through a finger lever along line A—A ofFIG. 1, and

FIG. 4 shows a detail out of a side view of a finger lever, partly insection.

DETAILED DESCRIPTION OF THE DRAWINGS

The finger lever shown in FIGS. 1 to 4 is a sheet metal part made by ashaping process without chip removal and comprises the two end regions 1and 2 and a central region 3. The end region 1 comprises a first bottomwall 4 from which two side walls 5 and 6 extend in an upwardly openU-shape from the entire length of the finger lever. The bottom wall 4comprises a downward facing semi-spherical recess 7 that rests on asupport element, not shown. In the central region 3, the side walls 5and 6 comprise two axially aligned bores in which a cam roller 10 loadedby a cam is rotatably mounted through a rolling element crown ring 9 ona pin 8. In the end region 2, the side walls 5 and 6 are connected toeach other by a second bottom wall 11 and likewise form an upwardly openU-shape. A gas exchange valve 12 arranged in this region 2 bears withits stem against the bottom wall 11 and opens when the finger lever iscaused to pivot by the cam.

As can be seen further in the figures, the side walls 5 and 6 comprisein the end regions 1 and 2, i.e. in the region of the support elementand in the region of the gas exchange valve 12, retaining tabs 13 whichserve for a lateral guidance of the finger lever on the gas exchangevalve 12 and on the support element respectively. The retaining tabs 13are formed by partially punched-out sections 14 in the region of theside walls 5 and 6. By this is meant a severing of material withretention of a material continuity of the side walls 5 and 6 at onepoint. By a bending-over of this material punched free from the sidewalls 5 and 6 through 180° toward the support element and the gasexchange valve 12 respectively, it is not only the retaining tabs 13that are formed in the side walls 5 and 6 but also pockets 15.

It can be seen in FIGS. 2 and 3 that the retaining tabs 13 extendparallel to the side walls 5 and 6 but are inwardly offset therefrom.The retaining tabs 13 may have different shapes, for example as shown inFIGS. 1 and 4, they may be trapezoid in shape. FIG. 4 further shows thatthe retaining tabs 13 can be re-stamped, i.e. their shape can bemodified. The last-mentioned figure also shows that, after punching, theretaining tab 13 was originally semicircular in shape and was thenmodified into a into a trapezoid shape by re-stamping. FIGS. 1 to 4further show that the upper boundary of the punched-out section 14extends below the upper edge of the side walls 5 an 6, that is to say,the side walls 5 and 6 are not completely severed in their upperregions. In this way, the stability of the lever is assured. The figuresalso show that the shape of the upper edge of side walls 5 and 6 in theregion of the punched-out section 14 is matched to the contour of thepunched-out section, i.e., in FIG. 1, the upper part of the punched-outsection 14 is more or less parallel to the side wall 5, i.e. straight,while in FIG. 4, both the punched-out section 14 and the side wall 5have semicircular upper regions. FIG. 4 also clearly shows that theresidual cross-section 16 formed by the punched-out section 14 can bedisplaced into the pocket 15 by a shaping process. Finally, FIG. 3 showsthat in the region in front of and behind the retaining tabs 13, theside walls 5 and 6 are bent inward at right angles to improve stability.

What is claimed is:
 1. A finger lever for a valve train of an internalcombustion engine, said finger lever being made by shaping without chipremoval and comprising two side walls (5, 6) which are connected to eachother in a first end region (1) by a first bottom wall (4) to form anupwardly open U-shape, the first bottom wall (4) comprising a downwardlyfacing semi-spherical recess (7) for receiving a support element, saidside walls (5, 6) being connected to each other in a second end region(2) by a second bottom wall (11) to form an upwardly open U-shape, saidsecond bottom wall (11) comprising a contact surface for a valve stem ofa gas exchange valve (12), and the contact surface comprising lateralguides spaced apart from each other characterized in that, in the regionof the contact surface of the valve stem (12) and/or in the region ofthe semi-spherical recess (7), the side walls (5, 6) comprise partiallypunched-out sections (14) that are bent through nearly 180° toward thevalve stem (12) and/or toward the support element respectively, so thatretaining tabs (13) are formed for the lateral guidance of the fingerlever on the valve stem (12) and/or on the support element.
 2. A fingerlever according to claim 1, characterized in that the upper boundary ofthe punched-out section (14) is situated below the upper edge of theside walls (5, 6).
 3. A finger lever according to claim 1, characterizedin that the shape of the upper edge of the side walls (5, 6) in theregion of the punched-out section (14) is matched to the profile of thepunched-out section (14).
 4. A finger lever according to claim 1,characterized in that the residual cross-section (16) of the side walls(5, 6) formed by the partially punched-out section (14) is displacedinto the pocket (15) formed by the bent-over retaining tab (13).
 5. Afinger lever according to claim 1, characterized in that the retainingtabs (13) have a rectangular, a trapezoid or a semicircularconfiguration.
 6. A finger lever according to claim 1, characterized inthat the retaining tabs (13) are subjected to an after-treatment ofstamping.
 7. A finger lever according to claim 1, characterized in thatthe retaining tabs (13) are parallel to or are bent to extend at adefined angle to the side walls (5, 6).
 8. A finger lever according toclaim 1, characterized in that the retaining tabs (13) are parallel tothe side walls (5, 6) and are arranged inwardly offset from the sidewalls (5, 6).
 9. A finger lever according to claim 1, characterized inthat the upper edge of the side walls (5, 6) in the region in front ofand behind the retaining tabs (13) is bent inward at a right angle.